The Aquapolis set is the second e-Reader set. Continuing the e-Reader set standards introduced in Expedition, Aquapolis took it further and even had several cards which had two versions, both containing different e-Reader data. It is also the first set that seperates the Holographic cards out of the main card count in order to prevent Reverse Holographic versions of the Holographic cards clashing with their Non-Holographic counterparts. Counting all the cards in the set, this set is the biggest set in card historyThis set also introduced Crystal Pokémon to the game. Crystal Pokémon are Colorless typed Pokémon who have the ability for their type to change depending on the energy attached to them.